This invention relates to an apparatus and a method for providing a fibrous web with embossings on both sides, thereby creating a double-sided three dimensional embossed web.
The fibers to be used in the present invention comprise cellulosic fibers, wood fibers, mixtures with synthetic fibers including bicomponent fibers and synthetic fibers. The synthetic fibers may, e.g., be of polypropylene or polyethylene. Also glass fibers, rock wool fibers, and pretreated fibers may be used.
The invention also relates to the fibrous web itself. The embossing process is an in-line process by which the web formed is led through a so-called embossing calendar. The web may be a plastic web, a paper web or the like. It is also possible to emboss a multi-layer web.
The embossing calendar comprises an embossing roller and a cooperating pressure roller and between which the web is led in order to emboss one side of the web. If a double-sided embossing is provided, the web is led through a further embossing calendar having the embossing roller and the pressure roller arranged oppositely in relation to the positioning in the first embossing calendar. Thus, the prior technique results in a voluminous apparatus.
Serious problems occur if the double-sided embossing is effected simultaneously by the use of two embossing rollers. Thus, a great risk exists that the web will be broken in areas where two raised portions are arranged opposite each other in a central plane passing through the axis of rotation for the two embossing rollers. This risk for breaking or rupturing of the web is especially high when thin webs are embossed.
For many products it is a desire to have double-sided embossed webs and it is desired that such web could be rather thin. When having double-sided embossing the web would have a high quality in hand and feel and also in drapability. Thus, a sheet being embossed only at one side would have a very poor drapability, being governed by the non-embossed surface of the web. Moreover, a web being embossed only at one surface would feel more stiff and hard. Accordingly, it is said to have a poor hand feel. When embossing the web at both sides, the web will a lot of points around which the web is able to bend. This is the effect which gives the web a good hand feel and a good drapability. Such web is especially suitable for manufacturing cloths, curtains, wash cloths, diapers, and other products which should feel soft and pleasant for users or which should have a drapability to be compared with that of knitwear and textiles. The web may be manufactured with reinforcements nets, synthetic fibers included in the cellulosic fibers or be made solely of cellulosic fibers.
It is the object of the present invention to provide a fibrous web having an embossing on both surfaces in order to provide a web having a good hand feel and a good drapability, irrespective of the thickness of the web.